When clicking in a handle (in blue in the image below) that allows to rotate a shape, you don't always click in the center of it. My question is how do you deal with this (Δx, Δy) small vector (in red) from the click position (blue cross) to the handle center (blue dot), during the drag.

  1. keep the same vector in the main coordinates system, it feels like the circle handle could rotate on his center. (lower blue cross in the rotated shape on the right)

  2. keep the blue cross at the same position, but in the handle coordinate system, there it feels more natural to me. (second blue cross in the rotated shape)

enter image description here

  1. I could also simply center the handle on the mouse pointer as soon as I start dragging. But it will make a quick 'noncontinuous' move at t=0 if you see what I mean. Of course in practice the handle isn't larger than 20 pixels, which is small, but still..

2 Answers 2


You don't.

You know the user's intention was/is to rotate the entire column thing around your origin point at the bottom of your drawing. So do that. You're just making bigger buttons for convenience and speed of interaction, not control zones like an X-Y pad.

  • I added a 3. case, maybe that's what you mean
    – caub
    Commented Oct 1, 2016 at 7:38

When you place a barrel on earth by putting its one of circular faces down, and try to pull it by holding onto an edge, it will start to move as well as gain slight rotation. If I understand you correctly, it is this intuitive feeling that you are trying to capture.

In real world, object tend to rotate when you pull them by holding on a point that is off center-of-mass. But, as pointed out by @Confused, we tend to simpify the experience, because in most cases, we know the intention of the user.

I assume that the question is not about a computer/mobile game where you may want to simulate real world experience.

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